Automatic dishwashing detergents (hereinafter ADDs) used for washing tableware (i.e. glassware, china, silverware, pots and pans, plastic, etc.) in the home or institutionally in machines especially designed for the purpose have long been known. Dishwashing in the seventies is reviewed by Mizuno in Vol. 5, Part III of the Surfactant Science Series, Ed. W. G. Cutler and R. C. Davis, Marcel Dekker, New York, 1973, incorporated by reference. The particular requirements of cleansing tableware and leaving it in a sanitary, essentially spotless, residue-free state has indeed resulted in so many particular ADD compositions that the body of art pertaining thereto is now recognized as quite distinct from other cleansing product art.
In light of legislation and current environmental trends, modern ADD products desirably contain low levels or are substantially free of inorganic phosphate builder salts and/or are concentrated formulations (i.e. 1/2 cup vs. full cup usage). Unfortunately, nonphosphated ADD products in technical terms may sacrifice efficacy, especially owing to the deletion of phosphate and, in some instances, chlorine mainstay cleansing ingredients. Concentrated or compact compositions similarly exhibit formulation problems.
Users of ADDs have come to expect all tableware will be rendered essentially spotless and film-free in addition to cleaning. In practice, this means avoiding film-forming components. The formulator will generally employ ingredients which are sufficiently soluble that residues or build-up do not occur. Again, while some ingredients may be adequate on grounds of cleaning, spotting and filming, solubility considerations may diminish their usefulness. Solubility considerations are even more acute with the newer "low usage", "concentrated", ADD compositions whose overall solubility can be less than that of conventional ("full cup") products.
It has generally been believed by the formulator of ADDs that inexpensive cleaning can be achieved via high alkalinity and/or high silicate levels (for example as provided by formulations comprising high percentages by weight of sodium hydroxide, silicate or metasilicate). Severe penalties can result in these compositions in terms of product corrosiveness to dishwashers and tableware, especially china and glassware and incompatibllity with other detergent ingredients. It is therefore highly desirable, at least in some phosphate-free compact ADDs, to achieve good cleaning end-results without resorting to the use of high alkalinity/high silicate.
Chlorine and peroxygen bleaches are effective for stain and/or soil removal. Chlorine bleaches while effective cleaners are omen not compatible with other detergent ingredients and/or require additional processing. Peroxygen bleaches on the other hand are less reactive, but such bleaches are temperature and/or pH dependent. As a consequence, there has been a substantial mount of research to develop bleaching systems which contain an activator that renders peroxygen bleaches effective in various wash liquor conditions. Also the conventional chlorine bleaches and peroxygen bleaches, i.e. perborate and percarbonate, have not been found to be effective in removing stains from plastics.
Another source of bleaching are the diacyl peroxides (DAPs). Although diacyl peroxides have been disclosed for use in the laundry and anti-acne area, they have not been employed in the ADD area. In the laundry field certain diacyl peroxides have been found to be effective in the removal of tea stains from fibrous material. In a dishwashing context however these diacyl peroxides have been found to be less effective than perborate and percarbonate on tea stain removal. Further, as discussed above, solubility of diacyl peroxides has been a concern in the laundry field as well.
It has been surprisingly discovered that DAPs can improve the stain removal performance of ADDs on plastics and china.
Further, it has been surprisingly found that the order of addition for the formulation containing water-insoluble diacyl peroxides is important in obtaining a better performing product.
It is further been discovered that the mixing of a water-insoluble diacyl peroxide with a dispersing agent prior to addition of other detergent ingredients yields a product with enhanced cleaning performance.
It is also been discovered that the performance is especially enhanced in a cold filled environment (European conditions).
The novel ADDs have the property of removing a wide variety of stains, including tea stain, fruit juice and carotenoid objected to by the consumer from plastic and china dishware. The compositions have other cleaning and spotlessness advantages such as enhanced glass care (i.e. reduction of cloudiness and iridescence negatives) and reduction of silicate/carbonate deposition filming negatives.